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Ampeg SVT makes after reassembling

#23
Well, I know that now.
What about the squeaking noise when turning up the treble controls. It is a constant higher pitch sound that goes away sudden when treble is turned down again. When ULTRA HI switch is engaged it occurs earlier then when this switch is off.
I have no idea where this comes from.
 
#26
PhantomBox said:
Instability with the tubes? What components could be oscillating?
Please help.....
Click to expand...

A bad tube could be the source of the problem.

Turn the offending control up just below the point where the noise starts. Then lightly tap the tubes with something like a chopstick. You may find one tube that easily rings at the offending frequency. Tap each tube to find the most likely candidate. Once you have narrowed it down, try replacing the suspect tube.

If this does not correct the problem, I suggest sending the amp to a qualified technician.
 
#27
Break the problem down. Start over, determine if it’s in the pre-amp or the power amp. Then examine each sub circuit in the half that has the issue. Look at every joint that you soldered. Wires that you moved could have broken.

Could be a tube as mentioned. Check that first. Could also be a tube socket contact.
 
#28
OK, I did as you said, got the squeaking removed from channel 2. I tighened the grip on the tube sockets female pins.
However, on channel 1 it's still present.
When I first took the preamp apart in order to get to the circuitry, and then reassembled it, the ceramic caps got bended quite a lot. I know these caps are hard to destroy unless a higher voltage then rated is applied (happened before), or if the ceramic disc brakes due to physical stress. Or it crambles off at the contact wires.
Could this be the case with my amp?
 
#29
PhantomBox said:
OK, I did as you said, got the squeaking removed from channel 2. I tighened the grip on the tube sockets female pins.
However, on channel 1 it's still present.
When I first took the preamp apart in order to get to the circuitry, and then reassembled it, the ceramic caps got bended quite a lot. I know these caps are hard to destroy unless a higher voltage then rated is applied (happened before), or if the ceramic disc brakes due to physical stress. Or it crambles off at the contact wires.
Could this be the case with my amp?
Click to expand...
Possibly, but not a likely cause.
 
#30
I finally solved the misterious squeaking. It was the bass I have in my workshop that is not shielded. It is a "Frankenstein" bass I build from spare parts and use to test the amps I repair. First time this happens. Who would have guessed...
I tried the amp with another bass and no issues, also used an electro-acoustic with piezo pickup (that one had feedback issues due to its construction) but sounded even cleaner.
Sooo, the Ampeg is ready to go.
And I got to get my Frankenstein fixed. My 1st name is Frank, by the way.
 
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